A flat object unstacking device comprises four main units:
a mail feed magazine, PA1 a mail holding device, PA1 a double pick separator, PA1 a transfer or take-off device.
The mail is stood on edge on a belt with its back against a plate. The belt and the plate are driven simultaneously so that the mail is moved towards the holding device. The belt leads to a sudden change in level, referred to hereinafter as the drop. The mail items then drop into a feed magazine adjacent the mail holding device.
The holding device has suction areas across which a perforated belt passes.
On leaving the holding device the mail passes across the suction area of the double pick separator on the opposite side of the belt. This unit retains mail items that might otherwise be entrained by friction by the preceding mail item so that only one mail item at a time can leave.
On leaving the double pick separator the mail is taken into a take-off device which constitutes an interface between the unstacking device and a sorting device.
French patent application No. 91 09431 of 25 Jul. 1991 in the name of this Applicant discloses a device for unstacking flat objects including a retaining unit serving as a double pick separator. This retaining unit is in the form of a suction head acting on the back of an unstacked mail item. It is on the upstream side of a transfer device comprising two drive belts and is activated when a flat object is taken up by this transfer device. The retaining unit is fixed to the frame of the feed magazine. This imposes a limit on the thickness of a flat object.
French patent application No. 91 04048 of 3 Apr. 1991 discloses a double pick separator device including a continuously acting suction unit having a flat side across which move the two flat objects to be separated, which are held against this flat side, and a scraper unit which can reciprocate perpendicularly to this flat side. The scraper unit comprises a casing inside which the pressure is lower than that in the suction unit, a carriage supporting the scraper unit casing, means for moving the carriage to apply the casing to the two contiguous objects and means for automatically retracting the carriage. This separator device can have the following drawbacks:
It may be desirable for the separator not to be retracted, for example in the presence of a floppy mail item, to prevent excessive deformation of the mail item, and this retraction, which is by a predetermined amount, prevents the processing of thick mail items.